A hard disk drive (HDD) is a non-volatile storage device that stores digitally encoded data on rotating platters that have an associated magnetic surface. A hard disk drive includes a spindle that holds at least one platter having a magnetic surface. At least a portion of the magnetic surface is magnetized with information thereon and a read head detects the magnetized portions of the magnetic surface to read data therefrom and a write head excites the magnetic surface to write data thereto. A HDD preamplifier typically controls the read and write operations of the HDD, which includes several different modes of operations (e.g., sleep, read, idle, write, head select, etc.). To change the operating modes of the HDD (e.g., sleep to read, read to write, etc.), a particular sequence of events is carried out to enable and/or disable devices of the HDD preamplifier. The HDD preamplifier includes timers to enable or disable the circuits of the HDD preamplifier to change the operating mode of the HDD.
FIG. 1 is an illustration of a timer 100 in a preamplifier of a HDD. In the operation of FIG. 1, an input 102 receives a voltage and either turns on or turns off a N-channel metal oxide semiconductor (NMOS) transistor 104. When the NMOS transistor 104 is turned on, the NMOS transistor 104 causes a current provided via a current source 106 to flow into a ground. As a result, a capacitor 110 is not charged. A comparator 108 that compares the voltage at the drain of the NMOS transistor 104 to a voltage reference VREF 112 outputs a low voltage. However, when the NMOS transistor 104 is turned off, the current from the current source 106 flows into the capacitor 110 where it is stored and increases the voltage of the capacitor 110. Initially, the comparator 108 outputs a low voltage. However, as the charge of the capacitor 110 increases, the voltage at the drain of the transistor 104 increases. After a period of time (i.e., a time delay), the voltage at the drain of the transistor exceeds the voltage reference VREF and the comparator 108 outputs a high voltage.